1. Field of the Invention
This invention relates generally systems and methods for transceiving information in a communications network, and more particularly to a method and apparatus for integrating multiple repeaters into a single collision domain without the need for external drivers and glue logic.
2. Description of Related Art
Recent advancements in the art of data communications have provided great strides in resource sharing amongst computer systems through the use of networks which offer reliable high-speed data channels. Networks allow versatility by defining a common standard for communication so that information independent of vendor equipment may be exchanged across user applications. The exchange of messages and data has been facilitated by the advent of Local and Metropolitan Area Networks. Remotely-located users communicate over the Local and Metropolitan Area Networks to access data and to communicate with other remote computer users. But as the popularity of networks has increased, so has the demand for performance. More sophisticated protocols are being established to meet this demand and are utilizing existing twisted pair wires in office buildings so that virtually all computer-literate users have access to resources with minimal expense.
As will be appreciated by those skilled in the art, communication networks and their operations can be described according to the Open Systems Interconnection (OSI) model which includes seven layers including application, presentation, session, transport, network, link, and physical layers. The OSI model was developed by the International Organization for Standardization (ISO) and is described in "The Basics Book of OSI and Network Management" by Motorola Codex from Addison-Wesley Publishing Company, Inc., 1993 (First Printing September 1992).
The primary standard for Local and Metropolitan Area Network technologies is governed by IEEE Std. 802. IEEE Std. 802 describes the relationship among the family of 802 standards and their relationship to the ISO OSI Basic Reference Model. Generally, IEEE Std. 802 prescribes the functional, electrical, and mechanical protocols, and the physical and data link layers for Local and Metropolitan Area Networks (LAN/MAN). The specification augments network principles, conforming to the ISO seven-layer model for OSI, commonly referred to as "Ethernet". In the hierarchy of the seven-layer model, the lowest layers, the so-called physical and data link layers, comprise functional modules that specify the physical transmission media and the way network nodes interface to it, the mechanics of transmitting information over the media in an error-free manner, and the format the information must take in order to be transmitted.
In such networks, nodes are connected to a bus and have multiple, or concurrent, access to the communications medium. However, a control technique is used to allow access to the communication medium and to resolve contention between the various users. Typically, a carrier sense, multiple access with collision detection (CSMA/CD) scheme is used. With CSMA/CD a node listens for activity and begins sending message packets when the node determines that no activity is occurring over the network. Sometimes simultaneous transmission by multiple nodes occurs. This results in collisions between the different message packets. When a node detects a collision, a signal is sent over the network to the other transmitting nodes. The affected nodes terminate their transmissions and probabilistically reschedule their next attempt to transmit. IEEE Std. 802.3 defines the standards for a bus utilizing CSMA/CD as a data link access method and is herein also incorporated by reference.
Typically, unshielded twisted pair cables or existing telephone wiring is used as the transmission medium to provide an economical solution to networking. However, the attenuation of signals transmitted over unshielded twisted pair cables increases as the distance between data terminal equipment becomes greater. Thus, repeaters are inserted in the twisted pair cables to facilitate greater distances.
While there are several LAN technologies in use today, Ethernet is by far the most popular. The definitions of the functions of an Ethernet repeater are contained in the IEEE 802.3 specification, which was incorporated by reference earlier. This standard defines attributes which can be used by a management function within an IEEE 802.3 Ethernet repeater to monitor network behavior.
In the past, repeaters were limited to a fixed number of ports thereby limiting the number of data channels. Accordingly, repeater manufacturers designed hardware which could be cascaded so that multiple repeater circuits could be integrated into a single hub. In order to allow multiple repeater circuits in a system to behave as a single hub, the repeaters must pass collision information in addition to routing data and clock signals. The collision information is passed between individual repeater circuits over an inter-repeater communication medium or backplane.
Wanting to further expand the number of ports that repeater circuitry can handle, repeater manufacturers now integrate multiple hubs so that the combination of hubs appears as a single large repeater. However, these multiple hub designs require external glue logic to distribute collision information among the hubs and the individual repeaters. There is a need, therefore, for a system that seamlessly integrates multiple repeaters into a single collision domain and which does not require external glue logic to implement a multiple hub design.